Method of making plywood tubing



Nov'.26,1946. y -r,. .-u.c j 2,411,542 I I METHOD F mklne-rmwqob TUBING "riled Sept. 10,"1942;- ,3 Sheets-Sheet 1 {WE/hon. 1 Theodore Lila/I I I A Tram/Ex;

Nov. 26, 1946. v 'r. a. ILCH METHOD OF MAKINGV'PI-A'WOOD TUBING Filed Sept. 1o,- 194g 5 Sheets-Sheet .2

' I mm, i 'T/repaprel' /d; A Worm/5y;

" is t ti he-1 plywood tubingl ,h -vingv of the,invention' is y proved process for wood tubing wherein the individual veneer peripheral compressive .jIn accordance with:

Patented Nov. 26,1946

mqw a empsbeatLN. 1., assiznor: 1, i

LWQ P United'states l'lywoodgorporatlon, afloorpoiratigiriolNetvIforh 1 mummies; lo fllirserial The invention relates to I into. the form orajpipe or tubingand more: particularly toseamless tubing. ,seam v this s e s.

incation, is intendedftoindicate the absence oi less) as hereinafter used} throughout extending from the any definite line or juncture "interim; to the exterior-surface joi ,the plpe or tubing j Y the inherent-advantages of plywo butewb h form has extremely valuable industrial; applica t n or in t n e. a stituting a. stronglcolumn or, by reasonor its great strength in heoptension as a pipe icrcone veying fluids underpressure. A further object whose lengthis considerably greaterandin fact may be ,many times 'greatenthanthe maximum transverse dimension orthe tube, the tubebeinz built up; from individual veneer, units. It is also an 7 objectv oi the invention are notsubjected tofany I stresses .during their assembly and particularly during the moldingoperation. Other objects will lama-fabric ted j direction and therefore considerable strength in Y hoop tension, th

invention produce such -a structural member cont r v e a i intoloose tubes, separately the manufactureoisuehply e I plurality of layers or veneers of plywoodwhich by :reason' of its tubular strength of th tubing sentencin great strength atransverse being ideallysuited for veyirig fluids under considerable pressure. The

of the wood is .laid up to run';

use as a column,whereas.ii the preponderance .pipe, it willbemoreuseiul for carrying fluids the thickness of the to provldeaplywood tube become evident from the further, moreidetailed description or the invention.

, While attempts have wood pipeor tubing, for

of -a' commerciall -utilizabletubing because oi:

instancerby assembling from lumber or ilat or bent "under pressure. Obviously been madeby prior 3.

- workers .to'produce amore or less seamlessply I I I for particular a commercial applications, intermediate. eflects .01;

strength can be secured, for; instance by altering tubing "orthe number of,

veneers or which the tubing-isconstituted.

.In its .gbroadest aspects, myginvention-consists 111 its final in the building up, and molding ultimate shape, a pipe or tubing, thatis, hollow structures whose length; is considerably 8rea ter than their diameters, by rolling up cylindrically and have been. suitably provided with ,layers' of. .ad hesive, sliding the thus rolled layers or veneers individually and. successivelyinside v a longitudie nallysplit steel mandrel of suitable length through oneo! its two 1 after release of the mandrel, insertlnga flexible fluid-tight membrane ;in'

the inherent stresses characterising the material" thus produced and because an is invol ed has been its deficiency in re thimt e on tu di e o and o e. es d s the un t ie rr nature '01" the product heretofore produced, the fabrication in;

' costs; and comparatively volved extremely, high small production yield. v H

duce economically .and

invention, I ban pro;

or tubing. in lengths for insta'nce,in'" the inordinate amount;

7 .in the/production ot such material. )The primary "cause or failure or such 18' p 'Qfill t tO-take its place'in' industrial applicationahowever,

with .egrcellent results so. far as v the necessary "j characteristics oifstreng'th are concerned,- anxiety or sizes oi plywood pipelf .up to as much asllieet,

been previously l fF sgl is a perspective view or a steelmandrel or split tube into which the, ingout of my. process are adaptedtobeplaced:

showing the steel mandrel, the

r V the shape of a cylindrical tube inside the. assembled veneers within ,the steel mandrel, and artergregate of mandrel, veneeraand membrane into affluid pressure, chamber, sealing" the. aggregate therein, applying heat, and pressure by means of the membrane tothe r impregnated or coate'd,to there! by-producejthe plywood tubing.

A particular embodiment of my novel process ofproducing a plywoodtubingand ofanap-, paratus suitable for carrying out such process, are illustrated in the ,accompanyingfdrawings, in

wh ch,

veneers inthe carry- 1Fig'.2 'is a cut-"away view, also in perspective,

I ositionwithln the mandrel, an the fluid-tight; membrane or rubber fabric sleeve within the tubing; is i of a plurality of, iv'enee'rs in con- 1 in succession, .a

7 I 7 open ends, contracting the split mandrel to enable the Ilnishedarticleto be withdrawn more rea'dilyafter the'molding and placing the an a k built-.upveneers to' cause the activation of the adhesive, withuwhich it has tubing constituted Fig. 6 is a section through the outsidecasing' or cooker with a modified sealing "arrangement for the veneers in the split mandrel.

Referring more particularly to the drawings, in which similar reference characters identify similar parts in the several views, sheets of plywood veneer coated with a suitable adhesive, after; drying, are curled or rolled up cylindrically and plate 25 of the casing. The bolts in position within an outer casing ll, being substantially centrally disposed therein by resting on a cradle IS. The mandrel assembly is pushed into the outer casing ll until the end of, the mandrel i abuts tightly against a gasket 20 positioned within andbearing against the head 2! of the casing i8. At the other end or the outer casing a companion plate "22, havingja gasket 23 onits inner face is pressed against the end of .the mandrel III, a plurality of bolts 24 being used to press the companion plate 22 toward the end being drawn up on theend plate, "a tightening and sealing of both endsor themandrel I0 is accomplishe slid one after the other into the split steel mandrel III which is provided throughout its length with a slot H of suitable width. The sheets of veneers are accurately templated to the proper width so that when they are slipped into the steel mandrel, through one of'its open ends, they will expand againstand completely overlie the interior surface thereof, having neither an overlapping nor an appreciable gap between their ad- Jacent free edges after they are forced into place. Each layer of veneers is accordingly a little narrower than the-preceding layer slid into the mandrel. The butt joints in the several layers of veneers are very carefully arranged sothat they do not occur at exactly thesame point in the periphery of the tubing to be formed, but are distributed at various points throughout the periphery of the tubing. As a'plurality of layers of veneers are used for the tubing, the completed molded tube will be, to all intents and purposes, seamless. s

After successive sheets of veneers have been slid into the steel mandrel I0 and all of the piles,

are in place, clamps i2, distributed appropriately throughout the length of the steel mandrel, are tightened by the bolts i3, giving the mandrel the exact inside diameter desired, and which will be the outside diameter of the plywood tubing to be produced. The layers of veneers within the steel mandrel constitute the pipe i4 and will, after the heat and pressure treatment hereinafterdescribed, form the molded plywood tubing; It will be understood that at the time that the mandrel is contracted, the veneers lie loosely within the mandrel, with many and considerable spaces between the individual veneers and between the first veneer and the mandrel. The degree of contraction of the mandrel is very small and is insufficient to create any peripheral compressive forces in any of the veneers. As already indicated, the purpose of the contraction of the mandrel is to provide a slight clearance between the same and the finished tube upon release of the mandrel at the end of the process.

A flexible, rubberized fabric. or similar fluid tight membrane in the shape of a cylindrical tube or sleeve I andwhich has both ofit's ends open, and is longer than the split steel mandrel I0, is then slipped or threaded into the steel mandrel within the assembled veneers, the ends of thesleeve being doubled backfor a short distance over theoutside of the mandrel, as shown at'Hi in Fig. 4, and an outer ring or sleeve-l1 is slipped on the folded back ends of the membrane to holdthe fabric in place.

The mandrel assembly,- now containing the plywood veneers and the sleeve, is then placed for an aperture 26 "this manner. the whole of the sleeve I! of the fluid-tight or rubberized fabric is sealed, except inthe center of the gasket 23 and a like apertur 21 in the gasket 20 at the head end of the casing l8. These apertures 28 and 21 are for the admission and egress of the heating and cooling fluids.

Afterthe sealing, thus accomplished, if fluid under pressure is admittedat one end, and the other end is closed thebag or sleeve 15 will be distended, forcing the veneerstightly against the interiorsurface of the mandrel I 0 .while the latter is in the transversely contracted condition. If these veneers have been previously coated with a heat-sensitive adhesive audit the fiuid introduced is sumci'e'ntly hot to activate the adhesive, the veneers will be tightly bound together. Pressure resulting from heating of air or generation of vapor in the-fibrous layers, is relieved through the narrowed slot ll whichstill remain'sin the mandrel after contraction, as shown in Fig. 3. After-sufilcient exposure to heat has been obtained, the end plate 22 can be removedand the split tube or'mandrel can'be withdrawn from v the outside-steel casing. If the clamping device or clamps are then released, the mandrel will spring to its normal, larger diameter, the plywood tube which-has been made can be withdrawn and is'ready for treatment, assembly'into useful articles or for sale without further treatment.

, Describing the operations above outlined, and referring now particularly to Fig. 5, when the sealing, as above described, has been'completed, air valve '28 and inlet valve 29 are opened, the exhaust valve 30 being closed. Exhaust valve 3| is-generally left open. Air pressure'through the inlet valve 29 is permitted to 'enter the'casing until the pressure, as indicated by air'pressure gage 32, is suificient to cause the veneers inside sureo'f approximately50 pounds per square inch has been found in practice'to be adequatefor this purpose. The air valve 28 is then closedand the steam valve 33-is' opened. Exhaust valve 30 is openedat the same time as the'steam valve 33;

The-steam passing into the casingthroughthe inlet valve 29 and inlet pipe 34 forces the air out, the temperature rising, as indicated by the thermometer 35, to approximately300" The pressure is maint'ainedpu'rely by the'pressure of the steam, or if it is desired tohave the 'pres'sure higher without increasing the temperature, ad-

ditional air-may be admitted'through the valve 28. 'A continual draining orbleeding of the systern'ispermitted through the exhaust valve III to prevent stratification and to maintain the desired temperature. p

S The outsidecasin'g l8 is provided at a number f points throughout itsleng'th with vents I8,

. which permit any pressure built up between the outer'casing II and thesteel mandrel ill to be 7 tion,

an alternative structure fQr 'attaining'the sealing continuouslyrelieved. "I have mum-mammmum of two'rof these wentsaor small holes'in'the Iouter'casing- :i 8115- desirable for thelproper carrying out or'mirprocesspw imparted to the assemblywithin "the: 'casingeto activate the thermo-sensitive adhesive, cooling in any, suitable manner isie'flected' if the adhesive or glue is Jathermo-plasticadhesive. ,If the-ad hesive or glue used'is thermo-se'ttinggit is only 4 necessary to release thelpressure.

:l'il'is then removediromthe outer casing ll; the i clamps i2 loosenedfth sleeve I! removed, and the finished plywood tubing withdrawn from the steel mandrel l0.

Thev mandrel The sizes of plywood tubing which may be For instance,- :plywood' tubing up to ;twenty+four inches-i :outside diameter could ."be' readilyfi-pro 'duced. So far as lengths are -'coneerned,-- uplto eleven feethave been in commercialipro duction and in larger diameters even :greater lengths can I be produced with facility," economy, and s'atis- 'factory results; from thepoiht of view ofistren gth :in both longitudinaland transverse directions; I

I J While I have described hereinabove'a'specific iembodiment' of my invention, it is obvivaust-liat various changes in= thespecific;arrangement of the several parts of-theapparatus maysb'e made without @departing' from, ,my:' invention.- For instance, in v place of. thefiflexible ffluidtight s membrane or sleeve "I 5;:open at'zboth' endsvnecessitatr ing the doublirig back offitheexcess at each end, 3 there may be used a cylindrical tube very much like-an automobile inner tube with both. ends sealed. ,With such alternative structure, a valve the activation oi -lthe glue. t-

- It win beseen'mm the ainline-that.

providedva process: for? plywood ,tubing whrilf thetube ishulltilfifrom a plurality otzpliable-veneeriunits .wl*uchare inserted one by: one, and endwise, into, 'a" relatively, long,

longitudinally splitmandrel? the mandrel hav-" 6 .ing substantiallythe outer-contours and dimen- (inthe i-icourse ofgfthe telescoping: assembly of the ,veneer preparatory .to the inflation oi the sions' oiqthel'flnished-iplywood article; and that flexible membrane and likewise during the course 'oij-themolding; the veneer units'are not subjected to any peripheralvcompressiomj. e., no force is Y exerted on them fromrthe-outsideto compel-them to contract peripherallygiethe veneer units being atmost' subiected aside from the radial pressure --overlapping at the or the pressure normal 1 to their surfaces, to "a 'slight-peripheral tensio'm- Thereby bucklingof the' veneers is avoiddwhileatthe same time 'joints "01' the individual I ve-' of g 'thermo -sensitive adhesiveiicoated sheets of I iflbrousfl-ma't'erial into arelatively rigid cylindrical 80 casing ,iunti1 .,theilayers ,are built up ingtubular j l.- 'rnememod of forming ran integral molded seamless tubing'j=fromfijilbrous sheet material =whi'ch comprisesintroducing'a plurality: of layers Q, form against the interior surface of such casing, :the" layers being coiled" individually and introstem would be utilized at each end having difierrent sealing mechanism than that described. -1

.In Fig. 6, I have shown in scheni'atic'cross secas the layers of veneers are omitted, such of the mandrel andveneers- In suchalternative structure, a cylindricalvpressure tube Iii oimaduced endwise insuccessioninto-the casing,;land I being allowed expand in the casing; and assume, approximately the contour oft. the casing,

"applying ;;a tubular I membrane f interior-1y of the ia'sse'rn-bled-sheets, andedistending; the membrane 3 v by'a;heatrandfpressur rriediurn sufflcient to press.

* athez sheetsjagain'st the interior'ot*thecasing-td bond theasheets to' ea'ch;;other and toymold such sheets to theiconflgurationof; the casing; v a

' 2.;3'I'he methodi ofi formingw anintegralmolded seamless plywood .tubin'g" from wood veneers,

which-"comprises applying athermo-sensitive adhsive'ftoa plurality of wood veneers, introducing I I successively narrower stripsv oi such veneers one by *on'einto' a relatively rigid cylindrical casing through "one dium at a' pressure si'iiilcientto press the veneers outward against the interior of ,the casing to terial, for instance rubber, such as is used'in anj automobile inner seams of the tube being vulcanized, a :valve'stem H being provided ateachend of the tube. The tube can then be inflated to distend the same tube, is sealedatboth ends, a115,:

than diameter, ,which'icomprises "coiling a sheet against the layers of veneers, by'air and/or steampressure admitted and exhaustedthroughvalves 42, and subsequently deflated. The split man-i I ,dreliil, into which theveneers and sleeve or tube a v, have beenplaced is supported within the outer cooking casing in substantially the same manner a as heretofore described in connection with ,the

preterred embodiment of the apparatus. 3

Aside from the specific variation Just described,

g other alternative forms of structure-and details will be apparent to those skilled in the art. For

instance, while I have described a specific ar-" rangement oi plumbing for the introduction of 7 air and steam to the outer casing, it is'obvious'j that, without departingirom my invention. other,

methods of sealing the split steel mandrel with a its enclosed sheets'of veneer may-be used for the fapplicationof heat and pressure to the'jveneers old them-into 'a seamless plywoodtube. 3.;Process"for the manufactureof seamless,

multiply tubing-of -,cons iderably I greater length ameter less than the average" outside diameter of theflnished tube, inserting the so coiledsheet endwise into a long, relativelyrigid tubular manv drel having inside transverse dimensions sub l stantially equal to the outside transverse dimensions of the flnishedtube, and allowing the coiled sheet to expand within the mandreland, assume a tubular contour similar. to that of the mandrel interior and substantially [free irompressure stresses in the peripheral direction, similarly coil ingand individually and successively'inserting into the mandreliin endwise fashion an additional sheet'or sheets of flexiblematerial, the

: subsequently coiled sheets being allowed to expand against the previously inserted sheet within the mandrel, there being provided a layer of adhesivebetween adjacent sheets, thenheating the assembled sheets and applying fluid pressiu'e bring them .tethe nnai molded "condition by i end thereof,'iapplying an expansible membrane interiorly of the assembled veneers, and distending the membranewith a heated mefrom the interior of the .mand'rel outwardly against the so te'escoped. fibrous tubesato' cause activation of the adhesive and mold the sheets 01' ilexible material'against the interior surface of the mandrel and into an integral multi-ply tube, and'removing the tube from the'imandrel.

4.- Process for the manufacture of seamless plywood tubing, which comprises coiling a wood veneer '-.nit to an average outside diameter less neer units being each allowedto expand against the previously inserted unit-within the mandrel,

there being provided'a, layer of adhesive between adjacent units, and then heating the veneers and applyin fluid pressurefrom the interior of the mandrel outwardly against the so telescoped veener tubes to cause activation of the adhesive andmold the veneer aggregate against the interior surface of the mandrel and into an integral multi-ply-tube, and removing the plywood tube from the mandrel.

5. Process for the manufactureof' seamless plywood tubing'which comprises cutting individual veneers to suitable dimensions, applying a thermo-sensitive adhesive to said veneers, coiling, in succession; such individual cut veneers about a longitudinal axis until the. longitudinal edgesoverlap, the temporary tubes thus produced being o1"a diameter less than the final diameter of the molded seamless plywood to be produced,

providing w'tubuiar mandrel and insertig such temporary tubes enclwise and in succession into the mandrel, permitting the veneers to expand within the mandrel whereby they assume a tubular shape with the longitudinal edges of each veneer tube in contiguous relation, inserting a flexible fluid-tight tubular membrane inside the assembled veneers within the mandreL'applying heat and suillcient pressure, byineans of said membrane to the built-up veneers'to cause the activation of the adhesive and thereby mold the assembly of theiveneers into an integral plywood tube having external dimensions corresponding to the internal dimensions of the mandrel, and removing the molded seamless plywood tube from the mandrel. a I 6. Process for the manufacture of seamless plywood-tubing, which comprises cutting indlvidual veneers to suitable dimensions, said veneers being provided upon certalnof their outer surfaces with a thermo-sensitive adhesive, coiling,

"in'succession, such individual cut veneers about 'alongitudinal axis until the longitudinal edges overlap, the temporary tubes thus produced being vof a diameter less than theflnal diameter of the molded seamless plywood tube to be produced, in-

sertin such temporary tubes endwise, and in succession, into a tubular mandrelwith theirlongitudinal joints in staggered :relation, permitting theveneers to expand within the mandrel whereby they'assume atubular shape with the longitudinal edges of: each veneer in contiguous relation, inserting a flexible fluid tight tubular membrane inside the assemblediveneers within the mandrel, applying heat and pressure by means of said membrane to the built-up veneers to cause activation of the adhesive and thereby mold the assembly. oi-'veneers into an integral plywood tube while venting air andvapor through the mandrel, and removing the molded seamless plywood tube from the mandrel.

" THEODORE EDWARD K. 

